1. Field of the Invention
The present invention relates to a continuous mold for a continuous casting plant and in particular for a continuous steel casting plant, where the inner walls of the mold are constructed of copper and/or of a copper alloy, and where the inner walls are provided with a wear resistant layer at its inside toward the mold hollow space.
It is known to provide the inner walls of a mold with wear resistant layers such as for example by way of explosion plating, electrolytical application, or by spraying. These known molds are provided with wear resistant layers covering the complete extension of the side walls, compare for example German Patent Applications Laid Open De-Os No. 2,625,914, DE-OS No. 2,838,296, DE-OS No. 2,822,004; Austrian Patents At-PS No. 322,756, AT-PS No. 360,684 and German Patent Application Laid Out DE-AS No. 1,284,051. These references concern continuous casting molds where the copper walls are provided with a material which is of a different chemical composition as compared with the mold base material. It is further known from Austrian Pat. No. 322,756 that the material deposed on the base material of the mold extends only over part of the mold. The German Patent Application Laid Open DE-AS No. 2,625,914 teaches a mold where the side walls at least in part provide a first and second layer, which are more wear resistant than the forms themselves. In general, in these known molds the heat transfer between the melt or, respectively, the casting shell and the inner walls of the mold covered with wear resistant material is disadvantageously affected.
In order to avoid affecting the heat transfer too much, the thickness of the wear resistant layer has been kept as low as possible and it was always kept to less than 1.5 millimeters. In case the wear resistant layer is applied onto the inside walls of the mold by electrolytic deposition then the layer thickness is kept even lower since the electrolytic process is an expensive procedure and the layer thickness amounts to at most a few tenths of a millimeter. This results in a further disadvantage as it has been found that a shape deviation of at least about 2 millimeters of the mold side walls begins to seriously affect the quality of the continuously cast material, such that one had to replace the wear resistant layer before the reaching of the maximum allowable deviation in the shape of the form, that is at the point where the thin wear resistant layer had been used up.
It is also known to furnish the inner walls of the mold with a very thin coating such as a chromium plating applied because of metallurgical reasons. Such a layer does not serve as a wear resistant layer since it is worked off by the casting shell within a short time. The purpose of this layer is to protect the melt from picking up copper from the walls of the mold.
The application of a wear resistant layer onto a mold inner wall always results in straining of the inner walls of the mold, which requires countersteps to be taken.